The present invention relates generally to cooking apparatus and, in a preferred embodiment thereof, more particularly provides a gas fired convection cooking oven which is provided with an improved air delivery and heat exchange section.
Cooking ovens in which heated air is continuously recirculated through a cooking chamber, to cook food items supported therein, are commonly referred to as "convection" ovens. A motor-driven fan impeller positioned within the oven housing is typically utilized to create the recirculating air flow through the cooking chamber, and cooking heat is conventionally transferred to the recirculated air by means of a gas burner whose combustion products are flowed directly into the fan impeller and/or flowed through a heat exchanger operably interposed in the path of the recirculating air.
A conventional direct-fired convection oven of this general type is illustrated in U.S. Pat. No. 4,648,377 to Van Camp. In the Van Camp oven a centrifugal fan impeller is positioned behind a single metal baffle plate vertically secured within the oven housing and generally defining a side boundary of the cooking chamber. The baffle plate has a central return opening through which recirculating air is returned from the cooking chamber to the fan impeller inlet, and peripheral edge passages through which heated air is forced by the fan impeller into the cooking chamber.
Circumscribing the fan impeller behind the baffle plate is a bifurcated heat exchanger structure having upper and lower manifolds respectively positioned above and below the fan, and a pair of generally U-shaped flow tubes positioned on peripherally opposite sides of the impeller and interconnected between the interiors of the upper and lower manifolds.
During operation of the oven the products of combustion from a gas burner are flowed sequentially into the lower manifold, upwardly through the tubes, and into the upper manifold. Air radially discharged from the impeller is flowed outwardly across and is heated by the external surface of the heat exchanger before being forced through the baffle plate peripheral openings into the cooking chamber.
The burner combustion products entering the upper manifold are discharged therefrom through a downward extension thereof positioned between the central baffle plate opening and the impeller inlet. The discharged combustion products are mixed with return air being drawn into the impeller, thereby directly transferring residual combustion product heat to the recirculating air flow. In alternate embodiments of the Van Camp oven, the upper manifold is eliminated and the open outer ends of the flow tubes are bent inwardly to a position directly in front of the impeller inlet to discharge burner combustion products directly into the impeller inlet.
Despite the apparent heat transfer efficiency of these air delivery and heat exchange structures, they have several inherent limitations and disadvantages. For example, they are fairly complex and relatively expensive to fabricate, assemble and install, thereby increasing the overall cost of the oven. Additionally, access to the fan impeller for cleaning, repair or replacement is somewhat inconvenient because the impeller is positioned behind the baffle plate, which is secured at various locations thereon to the interior of the oven housing, and is also partially blocked by the upper manifold or, as the case may be, outer end portions of the flow tubes. Thus, an appreciable amount of disassembly, and subsequent reassembly, is required to service the fan impeller.
Other conventional gas or electrically heated convection ovens having one or more of these disadvantages and limitations are representatively illustrated in U.S. Pat. No. 3,710,775 to Tamada et al; U.S. Pat. No. 3,991,737 to Del Fabbro; U.S. Pat. No. 4,108,139 to Gilliom et al; U.S. Pat. No. 4,467,777 to Weber; and U.S. Pat. No. 4,671,250 to Hurley et al.
It is accordingly an object of the present invention to provide a gas fired convection oven having an internal air delivery and heat exchange structure which may be easily, rapidly and inexpensively fabricated, assembled and installed and provides rapid and complete access to the fan impeller from the interior of the cooking chamber.